Conditional access system for local storage device

ABSTRACT

A technique for selectively inhibiting a video recorder from recording and/or reproducing those television programs, which are not authorized for viewing. Authorization data associated with respective television programs that are receivable by the recorder and indication of whether that program is authorized for recording and/or reproduction, is received by the recorder prior to (or multiplexed with) the television program and is stored thereat. When the television program is received, the stored authorization data associated with that is read to determine if the received television program is authorized for recording and/or reproduction. If not, the recorder is inhibited from recording and/or reproducing that unauthorized television program.

BACKGROUND OF THE INVENTION

This invention relates to selectively inhibiting television receivingapparatus from recording programs, received as digital video data, whichare not authorized for viewing.

Techniques have been proposed heretofore to permit viewers toselectively enable and disable television receiving apparatus to preventunauthorized television programming from being recorded and/orreproduced. With the introduction of the digital image communicationsystems such as the digital cable TV (CATV) systems, many services canbe provided that were previously unheard of with the conventional TVbroadcasting and CATV systems. The digital CATV systems not only provideconventional TV images, but can provide such services as electronic mailand electronic banking.

In the digital image communication systems, image storage devices arepreferably incorporated into a conventional television receivingapparatuses. This enables the viewer to watch a television program on aparticular channel while simultaneously recording television programsthen being broadcasted on other channels in the image storage device;which can be reproduced later by the viewer.

The digital cassette tape recorder (hereinafter referred to as digitalVCR) performs processing, such as parity code addition, ECC, formatting,modulating and so forth on video signals that have been highlyefficiently coded. Thereafter, one or more rotating heads of the digitalcassette tape recorder records the digital video signals on a magnetictape. The digital cassette tape recorder also performs playbackprocessing, such as demodulating, format decomposing, error correctionand so forth on the signals played back from the magnetic tape so as toreproduce the digital video signals.

The digital cassette tape recorder may be incorporated into aconventional television receiver or into a decoder of the type typicallyused in cable television or direct satellite broadcast systems. Suchdecoders or converters are known and, consistent with industry usage,are referred to herein, as set-top converters.

In addition, in the digital CATV system, data in which a plurality ofprograms have been time-division multiplexed are transmitted. Normally,one program channel is selected by a television receiving device todisplay or store the program on that selected channel. However, programsbroadcast on other channels at the same time as the selected programcannot be viewed or recorded for later viewing by that televisionreceiving device. Thus, it is desirable to record those programs so theycan be viewed later by the subscriber.

It is also desirable to record programs, such as movies, featurepresentations, pay-per-view, etc., transmitted from the source duringoff-hours, e.g., midnight, so those programs subsequently can be viewedby the subscriber upon receiving proper authorization.

OBJECTS OF THE INVENTION

Therefore, it is an object of the present invention to provide atechnique by which television receiving apparatus is selectivelyinhibited from recording those programs, received as digital video data,which are not authorized for viewing.

Another further object of this invention is to provide a technique bywhich television receiving apparatus is selectively inhibited fromreproducing those programs, recorded as digital video data, which arenot authorized for reproduction.

A further object of this invention is to provide a technique asaforesaid, which additionally decodes the recorded video data afterreproducing it from the recording medium.

An additional object of this invention is to provide a technique bywhich subscribers may rent or purchase videos using their televisionreceiving apparatus.

Various other objects, advantages and features of the present inventionwill become readily apparent from the ensuing detailed description, andthe novel features will be particularly pointed out in the appendedclaims.

SUMMARY OF THE INVENTION

In accordance with this invention, television receiving apparatus isselectively inhibited from recording those television programs which arenot authorized for viewing. Program information associated withtelevision programs that are receivable by the television receivingapparatus, such as title data representing the title of that program,rating data representing the content of that program, and authorizationdata indicating whether that program is authorized for recording and/orreproduction, is stored in the receiving apparatus. When digital videodata is received by the television receiving apparatus, theauthorization data associated with the television program correspondingto the received digital video data is read from memory to determine ifthe received television program is authorized for recording. If not, thetelevision receiving apparatus is inhibited from recording the receivedvideo data corresponding to that unauthorized television program. Asdescribed herein, a program cannot be recorded until it has beenpreviously authorized for recording by the commercial televisionbroadcast/distribution systems provider (e.g., enablement of particularprograms in pay-per-view application).

In a preferred embodiment, the received digital video data is encodedand the television receiving apparatus requires a scrambling key todecode the received digital video data. The decoded digital data is thenrecorded on a recording medium. As a preferred feature of the presentinvention, the scrambling key is transmitted in encoded form from asource to the television receiving apparatus.

In accordance with another aspect of this invention, televisionreceiving apparatus is selectively inhibited from reproducing thosetelevision programs which are not authorized for viewing. When a programrecorded on a recording medium is selected by the subscriber to bereproduced, the authorization data associated with the selectedtelevision program corresponding to the recorded digital video data isread from memory to determine if the selected television program isauthorized for reproduction. If not, the television receiving device isinhibited from reproducing the recorded video data corresponding to thatunauthorized television program. As described herein, a program cannotbe reproduced until it has been previously authorized for reproductionby the commercial television broadcast/distribution systems provider.

As a preferred feature of the present invention, the recording mediumcontains encoded digital video data and the encoded digital video datacorresponding to a selected program must be decoded before it can beviewed by the subscriber. The television receiving apparatus requires ascrambling key, which is also encoded, to decode the encoded digitalvideo data.

In accordance with yet another aspect of this invention, the recordingmedium is a digital video tape. The authorization information associatedwith the programs on the video tape is also stored on that video tape.The television receiving apparatus reads from the video tape theauthorization data associated with a selected program in the event thatcorresponding authorization data is not present in the memory. Thisfeature enables other television receiving apparatus to reproduceauthorized programs even if the authorization data associated with theselected program is not present in the memory of that other televisionreceiving apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description, given by way of example, and notintended to limit the present invention solely thereto, will best beunderstood in conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram showing a digital CATV system whichincorporates the present invention;

FIG. 2 is a block diagram showing the incorporation of the presentinvention in television receiving apparatus;

FIG. 3 is a block diagram representing the manner in which a televisionprogram is encoded by the head-end controller and decoded by televisionreceivers, for example, in a cable distribution or direct satellitebroadcast system.

FIG. 4 is a block diagram representing another manner in which atelevision program is encoded by the head-end controller and decoded bythe television receivers, for example, in a cable distribution or directsatellite broadcast system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is readily implemented by presently availabletelevision receiving apparatus and electronic components. The inventionfinds ready application in virtually all commercial televisionbroadcast/distribution systems, including over-the-air broadcasts, wiredcable transmission systems and direct satellite broadcast systems. As isconventional, set-top converters typically are used to receive anddecode television programs that are transmitted by cable systems or bydirect satellite broadcast systems. Normally, such set-top convertersare not needed to decode television programs that are transmitted byover-the-air systems. Set-top converters, like other televisionreceiving devices, include tuning circuits (either analog or digital)which are operable to tune to any one of the different broadcastchannels that may be received thereby. For example, if the set-topconverter is used in a cable transmission system over which 25 differentchannels of television programming are transmitted, the tuning circuitryincluded in the converter is adapted to select any one of such 25channels. Similarly, if the set-top converter is provided in a directsatellite broadcast system over which 150 different broadcast channelsof television programming are received, the tuning circuitry included inthe converter is adapted to select any one of those 150 differentchannels. The tuning circuitry included in conventional over-the-airtelevision receiving devices is, of course, adapted to select any of theover-the-air channels that normally are transmitted.

The present invention contemplates the transmission of programinformation data of the type that presently is available. Typically,such program information data is transmitted on a predeterminedbroadcast channel separate and apart from the broadcast channels overwhich television programming is transmitted. However, programinformation data that is multiplexed with television programminglikewise may be transmitted. The former transmission of programinformation data is known as out-of-band transmission; and the presentdiscussion refers to such out-of-band transmission in over-the-airbroadcast systems, cable distribution systems and direct satellitebroadcast systems. In one embodiment, the program information dataincludes the following information for each television program that istransmitted: the channel over which that television program istransmitted (i.e., the channel number), the name of the televisionprogram, and the rating data which represents the content of thattelevision program.

In addition to the foregoing information included in the programinformation data, it is a feature of the present invention also toinclude authorization data stored in the memory of the televisionreceiving apparatus indicating whether a television receiving apparatusis authorized to record and/or reproduce that television program. Forexample, the authorization data may include authorization statusinformation indicating whether the television receiving apparatus has alimited or complete authorization to reproduce a particular program. Theauthorization data may further include expiration date data whichrepresents the last date the television receiving apparatus with thelimited authorization is authorized to reproduce that program, and pricedata representing the additional payment required to change the limitedauthorization status of the television receiving apparatus to thecomplete authorization status.

Turning now to FIG. 1, there is illustrated a block diagram of a digitalCATV system which incorporates the present invention. A broadcastingstation 1 transmits broadcasting signals to a satellite 2 (for example,a broadcasting or communication satellite). These broadcasting signalsare re-transmitted to head-ends 3 disposed in individual service areas,each of which contains an antenna to receive the broadcasting signals, areceiving amplifier, an image source input portion (if necessary), amodulator to modulate the received broadcasting signals, and amultiplexer to multiplex the output of the modulator before it is outputto a transmission line.

Individual homes 4, i.e., subscribers to the CATV system, are connectedto the head-end 3 by a cable 5, which can be constructed as either acoaxial cable, an optical fiber cable, or a combination thereof. Thecable 5 is connected in a tree shape or in a star shape. A subscriber ofthe CATV system (home 4) is provided with a television receivingapparatus 6, which contains a tuner 10 for selectively tuning to adesired broadcasting channel and a digital VCR 7 to record or reproduceprograms. The reproduced digital video data which constitute the programreproduced from a recording medium are supplied to a display 8 whereatit is displayed to the viewer. It will be appreciated that display 8includes the usual video processing circuitry normally provided intelevision receiving apparatus to permit a television picture (andaccompanying audio information) to be displayed to a viewer.

The CATV system according to the present invention is not limited to theCATV system shown in FIG. 1. For example, a plurality of programproviders can transmit programs to the satellite 2. A CATV station maybe interposed between the satellite and the head-ends 3 to receivebroadcasting signals from the satellite 2 and relay those signals to thehead-ends by optical fiber cables. Each head-end is connected to manyhomes by optical fiber cables or coaxial cables. In addition, thepresent invention may be applied to a digital image communication system(such as a TV conference system) other than the digital CATV system.

The digital broadcasting signal generated in the head-end 3 contains aplurality of broadcast channels which are encoded for example usingmotion compensated inter-frame prediction coding techniques. Highlyefficient encoders are utilized in the head-end 3 (not shown) inaccordance with the MPEG (Moving Picture Experts Group) system that hasbeen adopted by the ISO (International Organization forStandardization). The encoded broadcasting signals are thentime-division multiplexed into a packet, which is digitally modulated,for example, using a PSK modulation technique.

Each packet is composed of 188 bytes with 4 bytes reserved for an IDcode. The ID code preferably is positioned at the beginning of eachpacket of time-division multiplexed data and contains programinformation data.

Each broadcast channel contains a plurality of programs which areencoded so that only authorized subscribers of the CATV system canreceive the broadcast programs. The encoding technique normally dependson each broadcast channel.

FIG. 2 illustrates a block diagram of television receiving apparatus 6which incorporates the present invention. The apparatus illustrated inFIG. 2 may be included in a set-top converter, a television receiver, avideo recorder or other conventional apparatus typically used to receiveand cause the display of television pictures. Control signals, whetherreceived by remote receiver (not shown) or generated by control elementsprovided directly on the television receiving apparatus, such as achannel selector (not shown), are coupled to a microprocessor (notshown) which controls the operation of a tuner 10 so as to tune to aselected television channel received thereby.

Although not described in detail, it will be appreciated that themicroprocessor may be a conventional microprocessor, such as arelatively inexpensive, small eight-bit controller or a powerful,high-speed microprocessor for example, a "486"-type microprocessor orPentium microprocessor manufactured by Intel Corp.

A signal of the selected channel is demodulated by a demodulator 11. Ifthe demodulated signal contains an error attributed to the communicationpath, the error is corrected by a forward error correcting circuit 12.The resultant signal is supplied to a conditional access circuit 13 todetermine if that signal constitutes a program that is authorized forrecording by the television receiving apparatus 6. The conditionalaccess circuit 13 reads from a memory (not shown) the authorization dataassociated with the program to determine if the television receivingapparatus is authorized to record that program. If there is noauthorization data in the memory associated with that program, theconditional access circuit 13 disables the operation of the digital VCR7 and/or causes an indication, such as the energization of an LED (notshown), to be displayed to the subscriber, indicating that thetelevision receiving apparatus is not authorized to record the receivedprogram. Such indication informs the subscriber to access theauthorization center of the cable distribution system to obtain thenecessary authorization to record the program. An additional level ofsecurity is provided by disabling the digital VCR 7 to preventunauthorized access to the digital VCR 7, i.e., programs stored therein.Moreover, the subscriber may call the authorization center to purchaseadditional services, such as, subscribing to additional broadcastchannels, pay-per-view programs, viewing videos on a pay-per-play basiswhere the viewer pays for each viewing of the video, etc.

In one embodiment of the present invention, the subscriber is providedwith a decryption device, such as in the form of a "card" similar to acredit card, a bank card, or the like, which includes decryption data aswell as an authorization representation recorded thereon. Suchdecryption data and authorization representation may be recorded in amagnetic stripe and, thus, may be changed or updated from time to time.Other forms of recording also are contemplated, such as opticalrecording of this information, storage in a solid state memory, etc. Forconvenience, the subscriber's decryption device described above isreferred to herein as a "smart card". The authorization representationthat may be recorded on the smart card preferably represents a thresholdmonetary amount which is sufficient to pay the requisite fee forrecording and/or reproducing the program (or to purchase otheradditional services from the cable distribution system). The subscribersimply places the smart card in a smart card receiving unit 15 of thetelevision receiving apparatus from which the requisite fee is deducted,thus obviating the need to place a call to the authorization center.

If the received signal of the selected channel has been encoded(scrambled), the demodulated signal is descrambled, provided that theprogram represented by that signal is authorized for recording by thetelevision receiving apparatus 6. The descrambled signal is supplied todigital VCR 7 to be stored on a magnetic tape. Also, the authorizationdata indicating whether the television receiving apparatus is authorizedto reproduce is supplied to the digital VCR 7 to be stored in anauthorization information area of the magnetic tape. The authorizationdata is desirably recorded multiple times on different tracks of themagnetic tape to insure reliability. Preferably, the authorization datais recorded twice on two different tracks of the magnetic tape to insurethat the authorization data is always present and accessible from themagnetic tape even if one of the tracks is damaged. The authorizationarea preferably is located at the beginning portion of the magnetictape.

The digital VCR 7 comprises a transport layer processing circuit 20, atrick play processing circuit 21, an error correction codeencoder/decoder 22, a channel encoder/decoder 23, and a tape headmechanism (or recording portion) 24. The transport layer processingcircuit 20 decodes data packets, each of which is composed of, forexample, 188 bytes and obtains program information from the ID portionof each packet. Data outputted by the transport layer processing circuit18 is written to a buffer memory (not shown).

The trick play processing circuit 21 reads the data from the buffermemory and is operable to record compressed image data (consistent withthe MPEG system) to effect special effects such as high speedreproduction or slow reproduction. For example, when high speedreproduction is performed, the trick play processing circuit 21 recordsintraframe data on a track of the record medium scanned by the rotatinghead. In the MPEG system, intraframe data is present in everypredetermined number of frames.

An output signal from the trick play processing circuit 21 is suppliedto error correction code encoder/decoder 22, the encoding section ofwhich performs error correction code encoding, such as adding paritydata. The output from the error correction code encoder/decoder issupplied to a channel encoder/decoder 23, the encoding section of whichmodulates the output signal of the error correction code encoder/decoderfor recording. The output from the channel encoder/decoder 23, which isrecord data, is supplied to the tape head mechanism portion 24 forrecording on the magnetic tape by a rotating head. The tape headmechanism portion 24 comprises a tape guide drum, a tape transport, anda servo circuit. The magnetic tape is wound around the periphery of thetape guide drum and is transported along a predetermined path. It willbe seen that a data storage device, such as a hard disk, a video disk ora magnetic disk, may be used with or in place of the digital VCR.

When a digital video tape is placed in the digital VCR 7, theconditional access circuit 13 determines if the television receivingapparatus is authorized to reproduce the program on that video tape. Theconditional access circuit 13 reads from a memory (not shown) theauthorization data associated with the program to determine if thetelevision receiving apparatus is authorized to reproduce that program.If there is no authorization data in the memory associated with thatprogram, then the conditional access circuit reads from an authorizationinformation area of the video tape in the digital VCR 7 and performserror correction consistent with error correction code, for example, C1code and/or C2 code. The authorization area preferably is located at thebeginning portion of the video tape.

The conditional access circuit 13 causes an indication, such as theenergization of a LED (not shown), to be displayed to the subscriber,indicating that the television receiving apparatus is not authorized toreproduce the selected program if the authorization data is not presentin either the memory or the video tape in the digital VCR 7.

Such indication informs the subscriber to access the authorizationcenter 32 (FIG. 3) of the cable distribution system to obtain thenecessary authorization to reproduce the selected program. If the smartcard is not utilized, the subscriber must call the authorization center32 to obtain the requisite authorization to reproduce the selectedprogram. If a smart card initialized with a predetermined monetarythreshold is utilized, the subscriber simply places the smart card insmart card receiving unit 15 of the television receiving apparatus fromwhich the requisite fee for reproducing the program is deducted, thusobviating the need to place a call to the authorization center 32.

If the conditional circuit 13 determines that the television receivingapparatus is authorized to reproduce the program recorded on the videotape in the digital VCR 7, the tape head mechanism 24 reproduces fromthe magnetic tape the video data constituting the authorized program,which is decoded and demodulated by the decoding section of channelencoder/decoder 23. The decoded data is supplied to the error correctioncode encoder/decoder 22, the decoding section of which performs errorcorrection consistent with the error correction code, for example, C1code and/or C2 code.

The decoded data is supplied to the transport layer processing circuit20 through the trick play processing circuit 21 to convert the format ofthe decoded data into the format of the received broadcasting signal sothat the MPEG decoder 14 can read and decode the decoded data. The MPEGdecoder restores the original video data and supplies it to a displayunit 8.

The manner in which a program received by the conditional access circuit13 is identified as being authorized for recording is explained inconjunction with FIG. 3. If a subscriber decides to subscribe to aparticular channel, the subscriber places a call to the authorizationcenter 32 of the cable distribution system requesting authorization ofthe subscriber's television receiving apparatus to record the programson that channel. Authorization data from the authorization center 32 iseither transmitted on a predetermined broadcast channel separate andapart from the broadcast channels over which television programs aretransmitted or is multiplexed with the television programs.Alternatively, with an initialized smart card, the subscriber merelyinserts the smart card into the smart card receiving unit 15 (shown inFIG. 2) and a microprocessor or CPU 33 of the conditional access circuit13 deducts the appropriate subscription payment from the balancerecorded on the smart card and thereafter sends requests to theauthorization center 32 via a modem 34 and a telephone line 29 totransmit the appropriate authorization data to the subscriber'stelevision receiving apparatus. This obviates the need to place a callto the authorization center 32 every time the subscriber wants tosubscribe to additional channels.

The smart card is initialized with a predetermined monetary amount, suchas $100, in response to the operation of a smart card initializationbutton (not shown) on the console of the television receiving apparatus,whereupon the microprocessor sends a smart card initialization requestsignal to the authorization center 32 via modem 34 and telephone line29. The appropriate authorization code is then transmitted from theauthorization center 32 to the microprocessor which records thepredetermined monetary amount on the smart card.

In one embodiment, prior to transmitting the program data to thetelevision receiving apparatus, the program data (video data) is encoded(scrambled) at the broadcasting station by a scrambler 30 with ascrambling key Ks. Preferably, each broadcast channel has a respectivelydifferent scrambling key Ks to scramble its programs. Since thetelevision receiving apparatus 6 cannot descramble the scrambledprogramming data without the proper scrambling key Ks, it is necessaryto transmit the scrambling key corresponding to a particular broadcastchannel to all television receiving apparatus authorized to receiveprograms on that particular channel. The television receiving apparatusstores the received scrambling keys in its memory (not shown).

When scrambled signals constituting a program are supplied to thetelevision receiving apparatus from the broadcasting station, theconditional access circuit 13 determines if those signals constitute aprogram that is authorized for recording by the television receivingapparatus. If the conditional access circuit 13 determines that thetelevision receiving apparatus is authorized to record that program, adescrambler 35 of the conditional access circuit 13 descrambles thereceived program with the stored scrambling key Ks using conventionaldescrambling techniques. The descrambled program data is then suppliedto the digital VCR 7 to be recorded on a video tape.

However, there is a risk in sending the scrambling keys in theiroriginal form because they can be easily intercepted by unauthorizedsubscribers, who then can receive (record) programs without receivingprior authorization from the authorization center 32. That is, "pirates"can view programs without paying the necessary subscription fee. Thus,in accordance with another embodiment of the present invention, thescrambling keys are encrypted (encoded or scrambled) before they aretransmitted to the authorized subscribers.

Prior to transmitting the program data to the television receivingapparatus, the program data is scrambled at the broadcasting station bythe scrambler 30 with the respective scrambling key Ks which is uniqueto the channel transmitting that program data. The scrambling key isitself encrypted at the broadcasting station by an encryption unit 36with a working key Kw. Preferably, each scrambling key is encrypted witha respectively different working key Kw. The television receivingapparatus 6 cannot descramble the scrambled program data with theencrypted scrambling key Ks. Hence, it is necessary to transmit theworking key Kw and the scrambling key Ks to enable the televisionreceiving apparatus to descramble the scrambled program data. Thetelevision receiving apparatus stores the received scrambling andworking keys in its memory (not shown).

When scrambled signals constituting a program are supplied to thetelevision receiving apparatus, the conditional access circuit 13determines if those signals constitute a program that is authorized forrecording by the television receiving apparatus. If the conditionalaccess circuit 13 determines that the television receiving apparatus isauthorized to record that program, a decryption unit 39 of theconditional access circuit 13 decodes (decrypts) the received scramblingkey with the proper stored working key and supplies the decryptedscrambling key Ks to the descrambler 35 of the conditional accesscircuit 13. Decoding (or decryption) of the scrambling key Ks iseffected by conventional decryption techniques utilizing the storedworking key Kw. The descrambler 35 then descrambles the received programwith the decrypted scrambling key Ks using conventional descramblingtechniques and supplies the descrambled program data to the digital VCR7 to be recorded on a video tape.

As with the scrambling keys, it is equally risky to send the workingkeys in their original or unencrypted form. Thus, in accordance with afurther embodiment of the present invention, it is preferable to encodethe working key Kw before it too is transmitted to the authorizedsubscribers.

Prior to transmitting the program data to the television receivingapparatus, the program data is scrambled at the broadcasting station bythe scrambler 30 with the respective scrambling key Ks which is uniqueto the channel transmitting that program data The scrambling key Ks isitself encrypted at the broadcasting station by the encryption unit 36with the working key Kw. Preferably, each scrambling key Ks is encryptedwith a respectively different working key Kw. Moreover, the working keyKw is itself encoded (encrypted) at the broadcasting station by anencryption unit 37 with a personal key Kp, which is unique to eachtelevision receiving apparatus. The television receiving apparatus 6cannot descramble the scrambled program data with the encryptedscrambling key Ks. It will be appreciated, therefore, that the workingand scrambling keys are also transmitted to the subscriber for eachauthorized channel and are stored in memory (not shown).

When scrambled signals constituting a program are supplied to thetelevision receiving apparatus, the conditional access circuitdetermines if those signals constitute a program that is authorized forrecording by the television receiving apparatus. If the conditionalaccess circuit determines that the television receiving apparatus isauthorized to record that program, a decryption unit 38 of theconditional access circuit 13 decodes the received working key Kw withthe pre-stored personal key Kp using conventional decoding (decryption)techniques and supplies the decoded working key Kw to the decryptionunit 39 of the conditional access circuit 13. The received scramblingkey Ks is then decoded by the decryption unit 39 of the conditionalaccess circuit 13 with the decoded working key Kw likewise in accordancewith conventional techniques (which may be the same as or different fromKw decryption) and the decoded scrambling key Ks is supplied to thedescrambler 35 of the conditional access circuit 13. The descrambler 35then descrambles the received program data using the decoded scramblingkey Ks and supplies the descrambled programming data to the digital VCR7 to be recorded on a video tape.

The keys Ks and Kw may be multiplexed onto one or more, or all of thechannels that are receivable by the television receiving apparatus ormay be transmitted over a separate, distinct channel. The three layersof encoding/encryption/scrambling insure a high level of security andprevent unauthorized recording of the transmitted programs.

Since in the embodiments described hereinabove, the program data isunscrambled prior to being recorded on the magnetic tape there is littleto prevent an unauthorized viewer from "tapping" the output ofdescrambler 35 and thereby watching the program as it is beingdown-loaded from the head-end 3 (shown in FIG. 1). For example, anauthorized subscriber of the channel may not be authorized to receive(reproduce) a special program (pay-per-view) on that channel. As anotherexample, an authorized subscriber may want to view (reproduce) moviesrecorded on magnetic or video tapes on a pay-per-play basis. However, aswill be described, television receiving apparatus in accordance with thepresent invention may be authorized for the recording of a program, butnot necessarily for the reproduction of that program.

The manner in which the television receiving apparatus is prevented fromreproducing a program even if it is authorized to record it isrepresented by the block diagram shown in FIG. 4. For simplicity,elements shown in FIG. 4 corresponding to those shown in FIG. 3 aredenoted by the same reference numerals and their description is omitted.

Depending on the method employed, the head-end 3 (shown in FIG. 1)either transmits the appropriate authorization data on a predeterminedbroadcast channel separate and apart from the broadcast channels overwhich program data is transmitted or multiplexes the authorization datawith the program data transmitted to the subscriber on the respectivebroadcast channels. Prior to encoding the program data as describedhereinabove with respect to FIG. 3, the program data is encoded(scrambled) to prevent an authorized viewer from "tapping" the output ofdescrambler 35 and thereby watching the program as it is beingdown-loaded from its head-end 3. Thus, in accordance with yet anotherembodiment of the present invention, prior to encoding the program dataas described hereinabove with respect to FIG. 3, the program data isencoded (scrambled) by a scrambler 41 (FIG. 4) with a modification keyKm. Preferably, each program is scrambled with a respectively differentmodification key Km. Since the television receiving apparatus cannotdescramble the scrambled program data without the proper modificationkey Km, it is necessary to transmit the modification key Km associatedwith a particular program to all television receiving apparatusauthorized to reproduce that particular program. The respectivemodification key Km is transmitted via the telephone line 29, or on apredetermined broadcast channel separate and apart from the broadcastchannel over which television program is transmitted, or is multiplexedwith the television program. The television receiving apparatus storesthe received modification keys in its memory (not shown) and/or in theauthorization information area of the video or magnetic tape or in thestorage device where the corresponding program is recorded. Prior torecording the received modification keys in the authorizationinformation area, the television receiving apparatus performs errorcorrection code encoding, such as adding parity data.

When a program is selected from a local store 45, e.g., a video tape inthe digital VCR 7, hard disk, video disk or magnetic disk, theconditional access circuit determines if the television receivingapparatus is authorized to reproduce the selected program. Theconditional access circuit reads from the memory (not shown) theauthorization data associated with the selected program to determine ifthe television receiving apparatus is authorized to reproduce theselected program. If there is no authorization data in the memoryassociated with that program, then the conditional access circuit readsfrom the authorization information area of the local store 45 andperforms error correction consistent with error correction code, forexample, C1 code and/or C2 code.

If the authorization data associated with the selected program ispresent in either the memory or the authorization information area ofthe local store 45, a descrambler 44 of the conditional access circuit13 descrambles the selected program with the stored modification key Kmusing conventional descrambling techniques. The descrambled program datais then supplied to the MPEG decoder 14, which restores the originalvideo data and supplies the video data to the display unit 8 whereat itis displayed to the viewer.

As previously discussed, there is a risk in transmitting keys or programdata in their original or unencrypted form. Hence, in accordance withstill another embodiment of the present invention, the modification keyis encrypted with the personal key Kp before it is transmitted to theauthorized subscriber.

Prior to transmitting the program data as described hereinabove withrespect to FIG. 3, the program data is scrambled at the broadcastingstation by the scrambler 41 with the respective modification key Kmwhich is unique to each program data. The modification key Km is itselfencrypted at the broadcasting station by the encryption unit 42 with thepersonal key Kp which is unique to each television receiving apparatus.The television receiving apparatus 6 cannot descramble the scrambledprogram data with the encrypted modification key Km. It would beappreciated, therefore, that the modification key is transmitted to thesubscriber for each authorized program and is stored in the memory (notshown) and/or the authorization information area of the local store 45.

When a program is selected from the local store 45, the conditionalaccess circuit determines if the television receiving apparatus isauthorized to reproduce the selected program. The conditional accesscircuit reads from a memory (not shown) the authorization dataassociated with the selected program to determine if the televisionapparatus is authorized to reproduce the selected program. If there isno authorization data in the memory associated with that program, thenthe conditional access circuit reads from the authorization informationarea of the local store 45 and performs error correction consistent witherror correction code, for example C1 code and/or C2 code.

If the authorization data associated with the selected program ispresent in either the memory or the authorization information area ofthe local store 45, a decryption unit 43 of the conditional accesscircuit 13 decodes (decrypts) the received modification key Km with thepre-stored personal key Kp and supplies the decrypted modification keyKm to the descrambler 44 of the conditional access circuit 13. Decoding(decryption) of the modification key Km is effected by conventionaldecryption techniques utilizing the pre-stored personal key Kp. Thedescrambler 44 then descrambles the selected program with the decryptedmodification key Km using conventional descrambling techniques andsupplies the descrambled program data to the MPEG decoder 14, whichrestores the original video data and supplies the restored video data tothe display unit 8 whereat it is displayed to the viewer.

The conditional access circuit 13 disables the operation of the digitalVCR 7 and/or causes an indication, such as the energization of an LED(not shown), to be displayed to the subscriber, indicating that thetelevision receiving apparatus is not authorized to reproduce theselected program if the authorization data associated with the selectedprogram is not present in either the memory or the authorizationinformation area of the local store 45. An additional level of securityis provided by disabling the digital VCR 7 to prevent unauthorizedaccess to the digital VCR 7, i.e., programs stored therein. The LEDindication informs the subscriber to access the authorization center 32of the cable distribution system to obtain the necessary authorizationto reproduce the selected program. If a smart card is not utilized, thesubscriber must call the authorization center 32 to obtain the requisiteauthorization to reproduce the selected program. If a smart cardinitialized with a predetermined monetary amount is utilized, then thesubscriber simply places the smart card in the smart card receiving unit15 of the television receiving apparatus, from which is deducted therequisite fee for reproducing the program, thus, obviating the need toplace a call to the authorization center 32.

The present invention contemplates the existence of a service by whichsubscribers may rent or purchase a video directly from their cableservice provider over the existing cable distribution system. Duringoff-hours (e.g., midnight or some other times specified by thesubscriber), the cable service provider periodically transmits allcurrently available movies (or only those movies satisfying thepreviously established subscriber's preference such as foreign movies,movies with G, PG, PG-13, R ratings etc.) with the correspondingauthorization data to the subscribers' television receiving apparatususing one or a plurality of broadcasting stations in the cabledistribution system. The television receiving apparatus records thesemovies (programs) received during a selected time interval on digitalvideo tapes to be viewed later by the subscriber. After recording thesereceived movies, the television receiving apparatus rewinds the tape tothe authorization information area to record the correspondingauthorization data. The selected time interval may be a day, a number ofdays, a week, a month, or a longer time interval. Typically, the timeinterval is a week and the television receiving apparatus thus storesmovies released during the past week.

The subscriber selects a desired movie (program) to view by selectingthe magnetic tape containing that movie (or by inserting the propervideo tape into the digital VCR 7). If the authorization data associatedwith the selected program is present in either the memory or theauthorization information area of the selected video or magnetic tape,the conditional access circuit determines if the television receivingapparatus has limited or complete authorization to reproduce theselected program. If such authorization status data for the selectedprogram is complete authorization, the television receiving apparatusmay reproduce the selected program indefinitely without limitation. Infact, complete authorization status associated with the selected programenables other television receiving apparatus to reproduce the selectedprogram even if the authorization data associated with the selectedprogram is not present in the memory of that other television receivingapparatus. Storing the authorization data on video tapes has the addedadvantage of allowing the viewers to share their videos with each other.

If the authorization status data of the selected program is limitedauthorization, then the conditional access circuit determines if therental period has expired for that video tape containing the selectedprogram. The conditional access circuit reads from the memory (notshown) the expiration date data associated with the selected program todetermine if the rental period has expired. If there is no expirationdate data in the memory associated with the selected program, then theconditional access circuit reads from the authorization information areaof the selected video or magnetic tape in the digital VCR 7. If therental period has not expired on the video tape containing the selectedprogram, the television receiving apparatus may reproduce the selectedprogram until the rental period expires.

The microprocessor 33 of the conditional access circuit 13 reads clockdata (not shown) to obtain the current date data. The microprocessorthen determines if the rental period has expired by comparing thecurrent date data and the expiration date data of the selected program.The television receiving apparatus no longer is authorized to reproducethe selected program if the expiration date of the selected program isprior to the current date.

If the rental period has expired, the television receiving apparatuscannot reproduce the selected program unless the rental period isextended or unless the authorization status of the selected program ischanged to complete authorization. The subscriber can extend the rentalperiod or change the status associated with the selected program tocomplete authorization by accessing the authorization center of thecable distribution system to authorize such change. Upon proper paymentby the subscriber, the authorization center transmits new authorizationdata associated with the selected program to the subscriber's televisionreceiving apparatus via the telephone line 29, or on a predeterminedbroadcast channel separate and apart from the broadcast channel overwhich television program is transmitted, or is multiplexed with thetelevision program. If a smart card is utilized, the subscriber merelyinserts the smart card into the smart card receiving unit 15 (shown inFIG. 2) and microprocessor 33 of the conditional access circuit 13deducts the appropriate fee from the balance recorded on the smart cardand sends the request to the authorization center 32 via modem 34 andtelephone line 29 to extend the rental period or change the status ofthe selected program to complete authorization. This obviates the needto place a call to the authorization center 32 every time the subscriberwants to extend the rental period or change the status of the selectedprogram.

While the present invention has been particularly shown and describedwith reference to a preferred embodiment, it will be readily appreciatedthat various changes may be made without departing from the spirit andscope of the invention. For example, the program information data neednot be multiplexed onto one or more, or all of the channels that arereceivable by the television receiving apparatus, but rather, may betransmitted over a separate, distinct channel. Also, although thetelevision receiving apparatus illustrated herein has been described asbeing present in a set-top converter for cable or direct satellitebroadcast distribution systems, or may be provided directly in atelevision receiver or video recorder, it is understood that suchapparatus may be disposed in a separate stand-alone unit.

It is intended that the appended claims be interpreted as including theembodiments discussed above with reference to the drawings, thosevarious alternatives which have been described and all equivalentsthereto.

What is claimed:
 1. Apparatus for selectively inhibiting a televisionreceiving device from reproducing from a recording medium video programswhich the apparatus is not authorized to reproduce, comprising:means forreading from a memory program information associated with programs thatare reproducible by said television receiving device, said programinformation including authorization data indicating whether saidapparatus is authorized to reproduce one or more of said associatedprograms; means for selecting a program to be reproduced from saidrecording medium; means for operating the means for reading to read fromsaid memory the authorization data associated with said selected programto determine if said apparatus is authorized to reproduce said selectedprogram, said authorization data including authorization statusinformation indicating whether said apparatus has a limited or completeauthorization to reproduce said selected program, expiration date datarepresenting the last date said apparatus with said limitedauthorization status is authorized to reproduce said selected program,and price data representing additional payment required to change theauthorization status of said apparatus with said limited authorizationstatus to said complete authorization status; means for inhibiting saidtelevision receiving device from reproducing said selected program if itis determined that said apparatus is not authorized to reproduce saidselected program; and means for reproducing from said recording mediumsaid selected program if it is determined that said apparatus isauthorized to reproduce said selected program.
 2. The apparatus of claim1, wherein the means for reading is operable to read the authorizationstatus information associated with said selected program to determine ifsaid apparatus has the limited or complete authorization to reproducesaid selected program; wherein the reproducing means is operable toreproduce from said recording medium said selected program if it isdetermined said apparatus has the complete authorization to reproducesaid selected program; and wherein the reading means is operable to readthe expiration date data associated with said selected program if it isdetermined said apparatus has the limited authorization to reproducesaid selected program.
 3. The apparatus of claim 2, further comprisingmeans for generating current date data and means for comparing thecurrent date data to said expiration date data associated with saidselected program to determine if said apparatus no longer is authorizedto reproduce said selected program; and wherein the means for inhibitingis operable to inhibit said apparatus from reproducing said selectedprogram if it is determined that said apparatus no longer is authorizedto reproduce said selected program.
 4. The apparatus of claim 3, whereinsaid means for inhibiting is operable to prevent said televisionreceiving device from accessing said recording medium.
 5. The apparatusof claim 1, further comprising means for modifying the statusinformation in response to a change status command transmitted from asource.
 6. Apparatus for selectively inhibiting a television receivingdevice from reproducing from a digital video record medium videoprograms which the apparatus is not authorized to reproduce,comprising:means for storing program information associated withprograms that are reproducible by said television receiving device in atleast one of a memory and a portion of said record medium, said programinformation including record medium identification data to uniquelyidentify said record medium and including authorization data indicatingwhether said apparatus is authorized to reproduce one or more of saidassociated programs; means for selecting a program to be reproduced fromsaid record medium; means for generating a list of authorized programsand said record medium identification data, each program beingassociated with respective record medium identification data thatidentifies the record medium on which that program is recorded; meansfor comparing the record medium identification data of said recordmedium to the record medium identification data of said generated listto determine if the authorization data associated with said selectedprogram is present in said memory and wherein said reading means isoperable to read from said record medium the authorization dataassociated with said selected program if it is determined that saidauthorization data associated with said selected program is not presentin said memory; means for determining from the authorization dataassociated with said selected program whether or not said apparatus isauthorized to reproduce said selected program; means for inhibiting saidtelevision receiving device from reproducing said selected program if itis determined that said apparatus is not authorized to reproduce saidselected program; and means for reproducing from said record medium saidselected program if it is determined that said apparatus is authorizedto reproduce said selected program.
 7. Apparatus for selectivelyinhibiting a television receiving device from recording and/orreproducing video programs which are not authorized for viewing,comprising:means for receiving a video program; a memory for storingprogram information associated with programs that are recordable andreproducible by said television receiving device, said programinformation including authorization data indicating whether saidapparatus is authorized to record and/or reproduce said receivedprogram, and said authorization data including authorization statusinformation indicating whether said apparatus has a limited or completeauthorization to reproduce said received program, expiration date datarepresenting the last date said apparatus with said limitedauthorization status is authorized to reproduce said received program,and price data representing additional payment required to change theauthorization status of said apparatus with said limited authorizationstatus to said complete authorization status; means for reading fromsaid memory the authorization data associated with said received programto determine if said apparatus is authorized to record said receivedprogram; means for inhibiting said television receiving device fromrecording said received program if it is determined that said apparatusis not authorized to record said received program; means for recordingsaid received program on a recording medium if it is determined thatsaid apparatus is authorized to record said received program; means forselecting a program to be reproduced from said recording medium; meansfor operating the means for reading to read from said memory theauthorization data associated with said selected program to determine ifsaid apparatus is authorized to reproduce said selected program; meansfor operating the means for inhibiting to inhibit said televisionreceiving device from reproducing said selected program if it isdetermined that said apparatus is not authorized to reproduce saidselected program; and means for reproducing from said recording mediumsaid selected program if it is determined that said apparatus isauthorized to reproduce said selected program.
 8. The apparatus of claim7, wherein the means for reading means is operable to read theauthorization status information associated with said selected programto determine if said apparatus has the limited or complete authorizationto reproduce said selected program; wherein the reproducing means isoperable to reproduce from said recording medium said selected programif it is determined said apparatus has the complete authorization toreproduce said selected program; and wherein the reading means isoperable to read the expiration date data associated with said selectedprogram if it is determined said apparatus has the limited authorizationto reproduce said selected program.
 9. The apparatus of claim 8, furthercomprising means for generating current date data and means forcomparing the current date data to said expiration date data associatedwith said selected program to determine if said apparatus no longer isauthorized to reproduce said selected program; and wherein the means forinhibiting is operable to inhibit said apparatus from reproducing saidselected program if it is determined that said apparatus no longer isauthorized to reproduce said selected program.
 10. The apparatus ofclaim 9, wherein said means for inhibiting is operable to prevent saidtelevision receiving device from accessing said recording medium. 11.The apparatus of claim 9, further comprising means for modifying theauthorization status information in response to a change status commandtransmitted from a source.
 12. Apparatus for selectively inhibiting atelevision receiving device from recording and/or reproducing videoprograms which are not authorized for viewing, comprising:means forreceiving a video program; a memory for storing program informationassociated with programs that are recordable and reproducible by saidtelevision receiving device, said program information including recordmedium identification data and authorization data indicating whethersaid apparatus is authorized to record and/or reproduce said receivedprogram; means for reading from said memory the authorization dataassociated with said received program to determine if said apparatus isauthorized to record said received program; means for inhibiting saidtelevision receiving device from recording said received program if itis determined that said apparatus is not authorized to record saidreceived program; means for recording said received program on a videorecord medium if it is determined that said apparatus is authorized torecord said received program; means for selecting a program to bereproduced from said video record medium; means for generating a list ofauthorized programs and said record medium identification data, eachprogram being associated with respective record medium identificationdata that identifies the record medium on which that program isrecorded; means for comparing the record medium identification data ofsaid record medium to the record medium identification data of saidgenerated list to determine if the authorization data associated withsaid selected program is present in said memory and wherein said readingmeans is operable to read from said record medium the authorization dataassociated with said selected program if it is determined that saidauthorization data associated with said selected program is not presentin said memory, and is operable to read from said memory theauthorization data associated with said selected program to if it isdetermined that said authorization data associated with said selectedprogram is present in said memory; means for operating the means forinhibiting to inhibit said television receiving device from reproducingsaid selected program if it is determined that said apparatus is notauthorized to reproduce said selected program; and means for reproducingfrom said video record medium said selected program if it is determinedthat said apparatus is authorized to reproduce said selected program.13. Method of selectively inhibiting a television receiving apparatusfrom reproducing from a recording medium video programs which theapparatus is not authorized to reproduce, comprising the stepsof:reading from a memory program information associated with programsthat are reproducible by said apparatus, said program informationincluding authorization data indicating whether said apparatus isauthorized to reproduce one or more of said associated programs, andsaid authorization data including authorization status informationindicating whether said apparatus has a limited or completeauthorization to reproduce one or more of said associated programs,expiration date data representing the last date said apparatus with saidlimited authorization status is authorized to reproduce said one or moreassociated programs, and price data representing additional paymentrequired to change the authorization status of said apparatus with saidlimited authorization status to said complete authorization status;selecting a program to be reproduced from said recording medium; readingfrom said memory the authorization data associated with said selectedprogram to determine if said apparatus is authorized to reproduce saidselected program; inhibiting said apparatus from reproducing saidselected program if it is determined that said apparatus is notauthorized to reproduce said selected program; and reproducing from saidrecording medium said selected program if it is determined that saidapparatus is authorized to reproduce said selected program.
 14. Themethod of claim 13, further comprising the steps of:reading the statusassociated with said selected program to determine if said apparatus hasthe limited or the complete authorization to reproduce said selectedprogram; reproducing from said recording medium said selected program ifit is determined said apparatus has the complete authorization toreproduce said selected program; and reading the expiration date dataassociated with said selected program if it is determined said apparatushas the limited authorization to reproduce said selected program. 15.The method of claim 14, further comprising the steps of:generatingcurrent date data; comparing the current date data to said expirationdate data associated with said selected program to determine if saidapparatus no longer is authorized to reproduce said selected program;and inhibiting said apparatus from reproducing said selected program ifit is determined that said apparatus no longer is authorized toreproduce said selected program.
 16. The method of claim 15, wherein thestep of inhibiting includes preventing said apparatus from accessingsaid recording medium.
 17. The method of claim 13, further comprisingthe step of modifying the status information in response to a changestatus command transmitted from a source.
 18. Method of selectivelyinhibiting a television receiving apparatus from reproducing from avideo record medium video programs which the apparatus is not authorizedto reproduce, comprising the steps of:reading from a memory programinformation associated with programs that are reproducible by saidapparatus, said program information including includes record mediumidentification data to uniquely identify said record medium andauthorization data indicating whether said apparatus is authorized toreproduce one or more of said associated programs; recording on saidrecord medium said program information associated with programs recordedon said record medium; selecting a program to be reproduced from saidvideo record medium; generating a list of authorized programs and saidrecord medium identification data, each program being associated withrespective record medium identification data that identifies the recordmedium on which that program is recorded; comparing the record mediumidentification data of said record medium to the record mediumidentification data of said generated list to determine if theauthorization data associated with said selected program is present insaid memory; reading from said memory the authorization data associatedwith said selected program to determine if it is determined that saidauthorization data associated with said selected program is present insaid memory; and reading from said record medium the authorization dataassociated with said selected program if it is determined that saidauthorization data associated with said selected program is not presentin said memory; inhibiting said apparatus from reproducing said selectedprogram if it is determined that said apparatus is not authorized toreproduce said selected program; and reproducing from said video recordmedium said selected program if it is determined that said apparatus isauthorized to reproduce said selected program.